The page you have linked to there is a high-level overview of the sorts of things that can be done with AWS to manage web hosting. When it says:

Websites that need to scale using load balancing, autoscaling, or external databases

you can surely do that but do not think that a single EC2 instance will give it to you. When they say "load balancing" they mean "use, deploy and pay for an Elastic Load Balancer to sit in front of your instances". When they say "autoscaling" they mean "use, deploy and pay for an Auto Scaling Group which will expand your fleet of EC2 instances behind the load balancer to match demand". You'll be paying handsomely for the external databases too, if you hadn't already guessed. It's a bit of work to set up such an environment but once done it runs pretty well. If you have the volume of traffic where you might need this then it is worth considering but it won't be cheap. Other providers will have similar offerings too, of course.